Ligaments are strong, tough bands that are not particularly flexible. The function of ligaments is to attach bones to bones and to help keep them stable. In the knee, they give stability and strength to the knee joint as the bones and cartilage of the knee have very little stability on their own.
Medial Collateral Ligament (or the tibial collateral ligament) – attaches the medial side of the femur to the medial side of the tibia and limits sideways motion of your knee.
Lateral Collateral Ligament (or the fibular collateral ligament) – attaches the lateral side of the femur to the lateral side of the fibula and also limits sideways motion of your knee.
Anterior cruciate ligament (ACL)– attaches the tibia and the femur. It’s located deep inside the knee and in front of the posterior cruciate ligament. It mainly serves to limit forward motion of the tibia relative to the femur. It also limits some rotation and sideways motion of the knee. The ACL can be torn with sudden pivoting motions of the knee.
Posterior cruciate ligament (PCL) – like the ACL, it attaches the tibia and the femur. It lies behind the anterior cruciate ligament. It mainly limits backward motion of the tibia relative to the femur. Like the ACL, it also limits some rotation and sideways motion of the knee. The PCL can be torn with a forceful landing on the shin.
Patellar ligament (or tendon) – attaches the kneecap to the tibia. It is less of ligament and actually a continuation of the quadriceps tendon.
Joint Capsule – a thick, fibrous structure that wraps around the knee joint. Inside the capsule is the synovial membrane which is lined by the synovium, a soft tissue structure that secretes synovial fluid, the lubricanr of the knee.
The pair of collateral ligaments keeps the knee from moving too far side-to-side. The cruciate ligaments crisscross each other in the center of the knee. They allow the tibia to “swing” back and forth under the femur without the tibia sliding too far forward or backward under the femur. Working together, the 4 ligaments are the most important in structures in controlling stability of the knee.